This Juno 60 was brought to me because it had had its memory replaced but it was still loosing it memory after a while. Opening it up revealed a bath of battery acid had eaten away at the RAM chips power pins, but not so much that they were disconnected. Meaning that when on the RAM appeared to work as the voltage drop across the corroded power pins didn’t get low enough to stop the memory from working when on but when in battery mode it would drop below the minimum threshold scrambling the memory. I also did a few things like cleaning the chorus buttons and cleaning the volume pot.
The two Ram chips with acid.